JPS63160393A - Manufacture of circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a method of manufacturing a circuit board in which a conductor wiring pattern is formed by etching a metal foil adhered to the board.

(b1 Background of the invention) It has been conventional practice to form a wiring pattern by bonding a Cu foil onto a substrate and etching the Cu foil. The formed film circuit board is LS
It is used in bonding substrates called film carriers or tape carriers for inner lead bonding of electronic components such as I-chips.

FIG. 2 shows a portion of this type of film circuit board. In the figure, 1 is a film substrate made of polyimide or the like, and 2 is a through hole for transporting this film substrate.

When manufacturing such a film circuit board, first, an opening 3 is created at a predetermined location on the film board 1 for bonding the LSI chip, and around that opening 3 is created to expose lead terminals when the area around the LSI is later cut. The four openings 4 are formed by punching. After performing C on such a film substrate, an LSI chip with lead terminals is formed by inner bonding an LSI chip to the tip of each lead terminal protruding into the opening 3, and punching out the part indicated by the dashed line 9. is manufactured.

FIG. 3 is a plan view of the LSI punched out as described above, and FIG. 4 is an enlarged sectional view thereof. In the figure, 6 is L
FIG. 5, which shows an SI chip and a plurality of lead terminals 5 are held by support rings 7 and connecting members 8, which are the remains of the film substrate 1, is a diagram representing another type of film circuit board. . Unlike the example shown in FIG. 2, in this case, a large opening 3 is formed at the location where the LSI chip is bonded, and the LSI chip is formed at the tip of the multiple lead terminals.
After bonding the I-chip, the inside of the opening 3 is cut as shown by the dashed line 9 to form a leaded LS.
We are manufacturing I. Figure 6 shows the face of the LSI cut in this way, and Figure 7 shows its enlarged cross section. As is clear from a comparison with FIG. 3, in this case no support is provided by a film base material such as a support ring.

(C1 Problem to be solved by the invention) In the film circuit board shown in FIG. However, even after the lead terminals are connected to the LSI chip, the support ring remains, and the adhesive layer remaining on the surface of the support ring This poses a problem.In other words, this adhesive layer has a slight problem with its insulation properties, and leakage current may flow in areas where the pitch between wiring patterns is small.Especially as a component of a device that requires high reliability. When used, this leakage between wiring patterns becomes a serious problem.

In the case of the film circuit board shown in Figure 5, the above-mentioned problem does not occur, but since the multiple lead terminals are not held by the support ring but only by the wide opening, the lead terminals may be deformed. This is a cause of a decrease in yield when bonding LSI chips.

There is also a two-layer structure circuit board in which a Cu pattern is formed directly on the substrate without using an adhesive layer, but this invention, which has a complicated process and high cost, It is an object of the present invention to provide a method for manufacturing a circuit board that eliminates problems caused by leakage between wiring patterns on the circuit board in a circuit board having a three-layer structure.

(Means for Solving Problem d1) The method for manufacturing a circuit board of the present invention involves bonding a metal foil onto an insulating substrate via an adhesive layer, and etching this metal foil to form a predetermined wiring pattern. After that, using this metal foil wiring pattern as a mask, the adhesive layer exposed on the substrate is removed by plasma etching.

(e) Function In the method for manufacturing a circuit board of the present invention, when a wiring pattern of metal foil is formed on an insulating substrate, it is patterned by etching.

At this time, the adhesive layer that adhered the insulating substrate and the metal foil was not etched and remained as it was.

Thereafter, the exposed adhesive layer on the insulating substrate is selectively removed by plasma etching the exposed adhesive layer on the insulating substrate using the wiring pattern as a mask. As a result, the adhesive layer remains only between the wiring pattern and the insulating substrate, and does not exist between the wiring patterns, thus solving the problem of leakage caused by the adhesive layer described above.

(f) Embodiment FIGS. 1A to 1C are diagrams showing the steps of a method for manufacturing a circuit board according to an embodiment of the present invention, each of which shows a cross section of the circuit board. In the same figure (A), 1 is the thickness 7
5 or 125 μm polyimide film substrate, and a 35 μm thick Cu metal foil is laminated on the surface of this film substrate via a 20 μm thick adhesive JWIO. A photoresist film is applied to the Cu foil surface of such a Cu foil laminate substrate, exposed through a photomask, etched, and then the Cu film is chemically etched. A conductive wiring pattern is formed as shown in B). Thereafter, the entire film circuit board is passed through an 02 plasma etching tank to perform plasma etching. As a result, the wiring pattern 5 made of the Cu film acts as a mask, and the exposed portions of the adhesive layer 10 are plasma etched and removed, as shown in FIG. 2C.

By performing the 02 plasma etching in this manner, the adhesive layer made of organic material is selectively removed.

In addition, in the 02 plasma etching process, not only the adhesive layer but also the polyimide film substrate is etched to some extent, but by controlling the oxygen partial pressure, etching time, temperature, frequency, output, etc., only the adhesive layer can be completely etched. Remove.

Thereafter, in order to improve rust prevention and soldering properties, Su and Au were coated on the wiring pattern made of Cu foil.

Apply solder plating, etc. to complete the circuit board.

(g1 Effect of the invention As described above, according to this invention, the adhesive layer for adhering the metal foil formed on the insulating substrate does not remain in areas other than the wiring pattern part, so the wiring using the adhesive layer No leakage occurs between patterns, and it can be applied to devices that require high reliability, where a slight leakage is a problem.In particular, when manufacturing a film carrier type LSI, it is possible to form a support ring. Therefore, there is no deformation of the leads, and there is an effect that the yield does not decrease when inner bonding the LSI chip.

[Brief explanation of the drawing]

1A to 1C are diagrams showing the steps of a method for manufacturing a circuit board according to an embodiment of the present invention, and FIG. Figures 3 and 4 show a film carrier type substrate that forms a support ring and a cut LSI with leads.
Figures 5, 6, and 7 are diagrams showing a film carrier type substrate that does not form a support ring and a cut LSI with leads. 1-Insulating substrate, 5-Metal foil, 10-Adhesive layer.

Claims (1)

[Claims] (1) After bonding a metal foil onto an insulating substrate via an adhesive layer and etching the metal foil to form a predetermined wiring pattern, use the wiring pattern of the metal foil as a mask to attach the metal foil to the substrate. A method of manufacturing a circuit board, characterized in that an exposed adhesive layer is removed by plasma etching.